Short wave communication circuit



Aug. 15, 1939. w. BUSCHBECK 2,169,352

SHORT WAVE COMMUNICATION CIRCUIT Filed April 9. 1937 r INVENTOR WERNEZUSC/IBECK BY ATTORNEY Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE snoar WAVE COMMUNICATION CIRCUIT tion of Germany Application April 9,

1937, Serial No. 135,840

In Germany May 2, 1936 7 Claims.

The invention relates: to an arrangement for suppressing disturbing upper harmonics in short wave transmitters.

In the accompanying drawing, Fig. 1 is a known type of short wave circuit given for purposes of exposition; Fig. 2 diagrammatically illustrates the principles of the invention; and Fig. 3 shows a system in accordance with the invention.

Fig. 1 shows two ordinary high frequency amplifier stages 5 and 6 connected with each other by a concentric energy line I. The grid current of the second tube 6 causes at the grid 8 of this tube the appearance of greatly distorted voltages with a large content in upper harmonics, and which ordinarily leak across the grid-cathode capacity of the tube and. across the capacities of the lead-ins so that they are not further amplified. However, in short Waves it happens that the grid-cathode capacity together with the leadin inductances, the stray-capacities, and the inductions and capacities due to the energy line form a blocking circuit for certain upper harmonics, so that at the grid a high voltage in upper harmonics appears which is further amplified. The primary object of the present invention is to eliminate such disturbances.

According to the invention, series: resonance members tuned to the operating wavelength, and damped eventually by a parallel resistance, are inserted in the grid lead-ins of high frequency amplifier tubes while avoiding additional line inductions and. stray capacities at the grids. Fig. 2 shows the principle of the present invention. In the grid lead, there is inserted the series connection of capacitance C and inductance L bridged by a resistor R. When assuming that asid from the unavoidable grid-cathode capacity, and the grid lead induction within the tube, no additional capacities or inductions appear by the introduction of these series members, the operating performance of this circuit is as follows:

At operating frequency, the series connection of L and C is in resonance, thus not influencing the wave to be transmitted. As regards upper harmonics, the oscillatory circuit formed of the tube capacity, the distributed lead capacity and induction, is damped.- to such a degree by the resistor R that in the case of resonance, high voltages cannot appear at the circuit. When operating with a single wave, the resistor R can be dispensed with, since simply by suitably dimensioning the series connection, detrimental resonances can be avoided.

In accordance with the invention, the above assumption that no additional capacities and inductions appear between the series resonance member and the grid of the tube, is put into practice by means of the following structure:

Fig. 3 shows the end of the concentric energy line. Item I represents the outer, and usually grounded conductor, item 2 is the energy conductor which conducts high frequency, and item 3 designates a tubular conductor inserted into the conductor 2 and insulated therefrom, and which together with the conductor 2 form a capacity. Within the tube 3 an inductance is provided connected at one side to tube 3, and which may eventually be variable. The free end of this inductance is connected directly with the grid connection point of the tube. As can be. seen, no stray capacities appear in this arrangement, since the oscillatory circuit is situated in the interior of the actual energy line. The inductance may be, for instance, a helix of ceramic material, whose surface is metallized in a spiral course, and whereby a sliding contact connected with the tube 3 and slidably arranged in the latter, moves along the windings of said helix. Arrow 4 diagrammatically represents such a sliding contact. When turning the ceramic part, the sliding contact will be moved thereby varying the value of the inductance connected with the capacitance.

What is claimed is:

1. A short wave transmitter circuit comprising a first amplifier stage having an anode and a second amplifier stage having a grid and a cathode, a circuit for suppressing disturbing high harmonic energy connected between said anode and said grid, said circuit having three concentrio tubes consisting of an outer tube, an inner tube and an intermediate tube, a connection between said cathode and said outer tube, a conductive helix within said inner tube connected at one end to said grid and at its other end to said inner tube, whereby the capacity between said inner and intermediate tubes combines with the inductance of said helix to form a series tuned oscillatory circuit tuned to the operating wave.

2. A short wave transmitter circuit in accordance with claim 1, including a connection from said outer tube to a point of zero radio frequency potential, and means within said inner tube for varying the inductance of said helix.

3. A short wave circuit comprising a first stage having an output electrode, a second stage having an input electrode, a circuit for suppressing disturbing high harmonic energy connected between said output and input electrodes, said circuit having a pair of concentric tubes, a connection between said output electrode and the outer one of said pair of tubes, an inductance in the form of a conductive member within the inner one of said pair of tubes, coupling paths from said inductance to both said input electrode and said inner tube, whereby the capacity between said pair of tubes combines with said inductance to form a series tuned circuit for the operating wave.

4. The combination with a series tuned circuit comprising an inner tubular conductor and an outer concentric tubular conductor spaced from said inner conductor in such manner as to provide substantially uniformly distributed capacitance therebetween, and an inductance element located within the inner tubular conductor and connected thereto at a point along the length of said inductance, of a source of energy coupled to said outer tubular conductor, and a utilization circuit coupled to said inductance element at another point.

5. The combination defined in claim 4, characterized in this that said inductance element is a helix one of whose ends is connected to said inner tubular conductor intermediate the ends of said tubular conductor, and the other of whose ends is connected to said utilization circuit.

6. A series tuned resonant circuit comprising inner and outer concentric hollow conductors spaced from each other in such manner as to provide substantially uniformly distributed capacitance therebetween, and a helical inductance element located within the inner hollow conductor and connected thereto at a point in the length oi said inductance element, the terminals of said tuned circuit comprising said outer hollow conductor and another point on said inductance, the capacitance between said hollow conductors forming a cylindrical condenser which together with the inductance of said helical element combines to form said resonant circuit.

7. A series tuned resonant circuit comprising inner and outer concentric hollow conductors spaced from each other in such manner as to provide substantially uniformly distributed capacitance therebetween, and a helical inductance element located within the inner hollow conductor and connected thereto at a point in the length of said inductance element, and means [or varying the effective value of said inductance element, the terminals of said tuned circuit comprising said outer hollow conductor and another point on said inductance, the capacitance between said hollow conductors forming a cylindrical condenser which together with the inductance of said helical element combines to form said resonant circuit.

WERNER BUSCHBECK. 

